Multiplexed Image Acquisition Device for Optical System

ABSTRACT

An image acquisition device including a first plurality of cameras arranged in a mutually spaced configuration, each having a field of view, each field of view lying in a plane and a second plurality of photon emitters arranged in a multiplicity of generally circumferential arrangements about each camera of the first plurality of cameras, at least one photon emitter within the generally circumferential arrangement directing light to a field of view of one of the first plurality of cameras that is not the closest field of view thereto.

FIELD OF THE INVENTION

The present invention relates generally to optical systems and moreparticularly to image acquisition devices for use in optical systems.

BACKGROUND OF THE INVENTION

Various types of optical systems including image acquisition devices areknown in the art.

SUMMARY OF THE INVENTION

The present invention seeks to provide a multiplexed, high resolution,high throughput, highly compact, easily manufacturable image acquisitiondevice for use in optical systems, in particular optical scanningsystems. The invention seeks to achieve these goals while at the sametime providing a relatively intense and both spatially and angularlysubstantially uniform illumination. The invention is particularly usefulfor fast and high accuracy reading of registration fiducial marks inproduction systems for manufacturing electronic substrates such asprinted circuit boards, semiconductor wafers, chip packaging substratesand solar panels.

There is thus provided in accordance with a preferred embodiment of thepresent invention an image acquisition device including a firstplurality of cameras arranged in a mutually spaced configuration, eachhaving a field of view, each field of view lying in a plane and a secondplurality of photon emitters arranged in a multiplicity of generallycircumferential arrangements about each camera of the first plurality ofcameras, at least one photon emitter within the generallycircumferential arrangement directing light to a field of view of one ofthe first plurality of cameras that is not the closest field of viewthereto.

Preferably, the mutually spaced configuration of the first plurality ofcameras includes a staggered array of rows of cameras, fields of view ofthe first plurality of cameras being at least partially overlapping whenviewed in a direction generally perpendicular to a direction of therows.

Preferably, the plane is a common plane occupied by each field of view.

Preferably, the plane coincides with a surface of a substrate to beimaged by the image acquisition device.

Preferably, each camera defines a camera axis, each generallycircumferential arrangement being centrally intersected by the cameraaxis.

Preferably, the photon emitter includes an LED.

Preferably, each generally circumferential arrangement includes at leastone ring of photon emitters.

Preferably, the at least one ring of photon emitters includes an innerring of photon emitters and an outer ring of photon emitters, the innerand outer rings being generally concentric.

Preferably, photon emitters including the inner ring emit light of afirst wavelength and photon emitters including the outer ring emit lightof a second wavelength, the first and second wavelengths being mutuallydifferent.

Preferably, the photon emitters including the inner ring are IR LEDs andthe photon emitters including the outer ring are amber LEDs.

In accordance with a preferred embodiment of the present invention, thefield of view to which light is directed by the photon emitter isentirely illuminated by the photon emitter.

Preferably, the image acquisition device also includes an illuminationplatform having an upper surface and a lower surface, the upper surfacebeing proximal to the first plurality of cameras, the lower surfacebeing distal from the plurality of cameras, the second plurality ofphoton emitters being mounted on the lower surface.

Preferably, a multiplicity of apertures is formed in the illuminationplatform, each aperture allowing viewing therethrough of the field ofview by the camera.

Preferably, each generally circumferential arrangement of photonemitters circumferentially surrounds each aperture.

Preferably, each camera includes a telecentric lens.

Preferably, each aperture is generally rectangular.

Preferably, the image acquisition device also includes at least onecollimator, for collimating the light.

Preferably, the at least one collimator is mounted on a collimatorboard.

Preferably, the collimator board is located adjacent to the illuminationplatform, between the illumination platform and the plane.

Preferably, the image acquisition device also includes at least onedeflecting element for directing the light output by the at least onecollimator.

Preferably, the at least one deflecting element is mounted on adeflector board.

Preferably, the deflector board is located abutting the collimatorboard.

Additionally or alternatively, the deflector board is formedmonolithically with the collimator board.

In accordance with a preferred embodiment of the present invention, theat least one deflecting element directs the light output towards asingle field of view.

In accordance with another preferred embodiment of the presentinvention, the at least one deflecting element directs the light outputtowards more than one field of view.

There is additionally provided in accordance with another preferredembodiment of the present invention an image acquisition deviceincluding a first plurality of cameras arranged in a mutually spacedconfiguration, each having a field of view, each field of view lying ina plane, a second plurality of photon emitters arranged in amultiplicity of generally circumferential arrangements, each generallycircumferential arrangement illuminating a field of view, each generallycircumferential arrangement, when projected on the plane of the field ofview illuminated thereby, circumferentially surrounding the field ofview and at least one photon emitter of at least one generallycircumferential arrangement directing light to at least one other fieldof view in addition to the field of view illuminated by the at least onegenerally circumferential arrangement.

Preferably, the mutually spaced configuration of the first plurality ofcameras includes a staggered array of rows of cameras, fields of view ofthe first plurality of cameras being at least partially overlapping whenviewed in a direction generally perpendicular to a direction of therows.

Preferably, the plane is a common plane occupied by each field of view.

Preferably, the plane coincides with a surface of a substrate to beimaged by the image acquisition device.

Preferably, each camera defines a camera axis, each generallycircumferential arrangement being centrally intersected by the cameraaxis.

Preferably, the photon emitter includes an LED.

Preferably, each generally circumferential arrangement includes at leastone ring of photon emitters.

Preferably, the at least one ring of photon emitters includes an innerring of photon emitters and an outer ring of photon emitters, the innerand outer rings being generally concentric.

Preferably, photon emitters including the inner ring emit light of afirst wavelength and photon emitters including the outer ring emit lightof a second wavelength, the first and second wavelengths being mutuallydifferent.

Preferably, the photon emitters including the inner ring are IR LEDs andthe photon emitters including the outer ring are amber LEDs.

Preferably, the image acquisition device also includes an illuminationplatform having an upper surface and a lower surface, the upper surfacebeing proximal to the first plurality of cameras, the lower surfacebeing distal from the plurality of cameras, the second plurality ofphoton emitters being mounted on the lower surface.

Preferably, a multiplicity of apertures is formed in the illuminationplatform, each aperture allowing viewing therethrough of the field ofview by the camera.

Preferably, each generally circumferential arrangement of photonemitters circumferentially surrounds each aperture.

Preferably, each camera includes a telecentric lens.

Preferably, each aperture is generally rectangular.

Preferably, the image acquisition device also includes at least onecollimator coupled to at least one photon emitter.

Preferably, the at least one collimator is mounted on a collimatorboard.

Preferably, the collimator board is located adjacent to the illuminationplatform, between the illumination platform and the plane.

Preferably, the image acquisition device also includes at least onedeflecting element coupled to the at least one collimator.

Preferably, the at least one deflecting element is mounted on adeflector board.

Preferably, the deflector board is located abutting the collimatorboard.

Additionally or alternatively, the deflector board is formedmonolithically with the collimator board.

In accordance with a preferred embodiment of the present invention, theat least one collimator is coupled to the at least one photon emitter ofthe generally circumferential arrangement directing light to at leastone other field of view in addition to the field of view illuminated bythe generally circumferential arrangement, the at least one deflectingelement directing the light to the at least one other field of view inaddition to the field of view illuminated by the generallycircumferential arrangement.

Preferably, the at least one deflecting element includes at least oneprism having a plurality of exit facets angled to direct the lighttowards the at least one other field of view in addition to the field ofview illuminated by the generally circumferential arrangement.

There is also provided in accordance with yet another preferredembodiment of the present invention an image acquisition deviceincluding a first plurality of cameras arranged in a mutually spacedconfiguration, each having a field of view, each field of view lying ina plane and a second plurality of photon emitters arranged in amultiplicity of arrangements about each camera of the first plurality ofcameras, at least one photon emitter of the second plurality of photonemitters directing light to a field of view of at least one of the firstplurality of cameras that is not the closest field of view thereto.

Preferably, the mutually spaced configuration of the first plurality ofcameras includes a staggered array of rows of cameras, fields of view ofthe first plurality of cameras being at least partially overlapping whenviewed in a direction generally perpendicular to a direction of therows.

Preferably, the plane is a common plane occupied by each field of view.

Preferably, the plane coincides with a surface of a substrate to beimaged by the image acquisition device.

Preferably, each camera defines a camera axis, each arrangement beingintersected by the camera axis.

Preferably, the photon emitter includes an LED.

Preferably, the image acquisition device also includes an illuminationplatform having an upper surface and a lower surface, the upper surfacebeing proximal to the first plurality of cameras, the lower surfacebeing distal from the plurality of cameras, the second plurality ofphoton emitters being mounted on the lower surface.

Preferably, a multiplicity of apertures is formed in the illuminationplatform, each aperture allowing viewing therethrough of the field ofview by the camera.

Preferably, each arrangement of photon emitters surrounds each aperture.

Preferably, each camera includes a telecentric lens.

Preferably, each aperture is generally rectangular.

Preferably, the image acquisition device also includes at least onecollimator, for collimating the light.

Preferably, the at least one collimator is mounted on a collimatorboard.

Preferably, the collimator board is located adjacent to the illuminationplatform, between the illumination platform and the plane.

Preferably, the image acquisition device also includes at least onedeflecting element for directing the light output by the at least onecollimator.

Preferably, the at least one deflecting element includes a thirdplurality of axicons.

Preferably, the third plurality of axicons includes an array of axiconshaving a density of between 4-10000 axicons/cm².

In accordance with a preferred embodiment of the present invention, thethird plurality of axicons includes axicons having mutually similaroptical properties.

In accordance with another preferred embodiment of the presentinvention, the third plurality of axicons includes axicons havingmutually different optical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 is a simplified illustration of an optical system including animage acquisition device forming a part thereof, constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIGS. 2A, 2B and 2C are simplified respective perspective, side andfront view illustrations of a portion of an image acquisition device ofthe type shown in FIG. 1;

FIG. 3 is a simplified illustration of an arrangement of photon emitterassemblies on an illumination platform in an image acquisition device ofthe type shown in FIGS. 1-2C;

FIG. 4 is a simplified conceptual illustration of a projection of photonemitters onto a plane of fields of view of cameras in an imageacquisition device of the type shown in FIGS. 1-2C;

FIGS. 5A, 5B and 5C are simplified respective illustrations of anillumination assembly and components thereof, forming part of an imageacquisition device of the type shown in FIGS. 1-4, constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIG. 6 is a simplified illustration of an optical illumination module ofan illumination assembly of the type shown in FIGS. 5A-5C;

FIG. 7 is a simplified illustration of light output from an opticalillumination module of the type shown in FIG. 6;

FIG. 8 is a simplified illustration of an optical illumination module ofan illumination assembly constructed and operative in accordance withanother preferred embodiment of the present invention;

FIG. 9 is a simplified illustration of light output from an opticalillumination module of the type shown in FIG. 8;

FIG. 10 is a simplified illustration of an optical illumination moduleof an illumination assembly constructed and operative in accordance withyet another preferred embodiment of the present invention;

FIG. 11 is a simplified illustration of light output from an opticalillumination module of the type shown in FIG. 10;

FIG. 12 is a simplified illustration of an optical illumination moduleof an illumination assembly constructed and operative in accordance withstill another preferred embodiment of the present invention;

FIG. 13 is a simplified illustration of an optical system including animage acquisition device forming a part thereof, constructed andoperative in accordance with another preferred embodiment of the presentinvention;

FIGS. 14A, 14B and 14C are simplified respective perspective, side andfront view illustrations of a portion of an image acquisition device ofthe type shown in FIG. 13;

FIGS. 15A, 15B and 15C are simplified respective illustrations of anillumination assembly and components thereof, forming part of an imageacquisition device of the type shown in FIGS. 13-14C, constructed andoperative in accordance with a preferred embodiment of the presentinvention;

FIG. 16 is a simplified illustration of an optical illumination moduleof an illumination assembly of the type shown in FIGS. 15A-15C;

FIG. 17 is a simplified pictorial illustration of light output from anoptical illumination module of the type shown in FIG. 16; and

FIG. 18 is a simplified plot of simulated light output from an opticalillumination module of the type shown in FIG. 16.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which is a simplified illustration ofan optical system including an image acquisition device forming a partthereof, constructed and operative in accordance with a preferredembodiment of the present invention.

As seen in FIG. 1, there is provided an optical system 100 including animage acquisition device 102. Optical system 100 may be any type ofsystem employing optical elements and benefitting from the inclusion ofan image acquisition device therein, such as, by way of example only, anoptical scanning system, optical inspection system, optical processingsystem or optical manufacturing system. Here, by way of example, opticalsystem 100 is shown to be embodied in a form typical of an opticalscanning system and image acquisition device 102 to be mounted thereon.It is appreciated, however, that this representation of optical system100 and the location of image acquisition device 102 therein isillustrative only and may readily be varied in accordance with thedesign requirements of optical system 100.

Image acquisition device 102 preferably includes optical elementsoperative to illuminate a substrate handled by optical system 100 and tosubsequently acquire an image thereof. Image acquisition device 102 maytherefore be termed an optical head 102. As seen most clearly at anenlargement 110 showing an enlarged view of optical head 102, opticalhead 102 preferably includes a first plurality of cameras 120 arrangedin a mutually spaced configuration, each camera having an associatedfield of view 122, each field of view 122 lying in a plane such as aplane 124. Plane 124 preferably coincides with a surface of thesubstrate to be imaged, such that fields of view 122 of cameras 120 lieon the substrate surface. In the case of a planar target, plane 124occupied by the fields of view 122 may be a common plane, within whichplane 124 all of fields of view 122 of cameras 120 lie. Alternatively,in the case of a non-planar substrate to be imaged, fields of view 122of cameras 120 may lie in more than one plane.

Optical head 102 further preferably includes a second plurality ofphoton emitters 130 arranged in a multiplicity of generallycircumferential arrangements 132 about each camera of first plurality ofcameras 120, which photon emitters 130 preferably illuminate fields ofview 122. It is a particular feature of a preferred embodiment of thepresent invention that at least one photon emitter within the generallycircumferential arrangement 132 of photon emitters directs light to afield of view 122 of one of the first plurality of cameras 120 which isnot the closest field of view to that photon emitter. Such anarrangement of plurality of photon emitters 130 with respect toplurality of cameras 120 allows plurality of photon emitters 130 toprovide wide-angle generally uniform illumination of field of views 122in a highly compact form factor, as is explained in greater detailhenceforth with respect to FIGS. 3 and 4.

Second plurality of photon emitters 130 is preferably mounted on anunderside 138 of an illumination platform 140. Illumination platform 140is preferably located beneath entrance facets 142 of lenses of cameras120, interfacing cameras 120 and fields of view 122, with underside 138of illumination platform 140 distal from entrance facets 142. Amultiplicity of apertures 144 is preferably formed in illuminationplatform 140, wherethrough light emanating from illuminated fields ofview 122 arrives at cameras 120. Second plurality of photon emitters 130is preferably circumferentially arranged with respect to apertures 144in a non-overlapping configuration, so as to illuminate fields of view122 without obscuring light emanating therefrom, as is detailedhenceforth with reference to FIG. 4.

Light emitted by plurality of photon emitters 130 may be directedtowards fields of view 122 in the manner described above by means ofvarious beam shaping optical elements 150, which optical elements 150may have collimating and/or deflecting functionalities. Such opticalelements 150 may be mounted on one or more boards, such as a collimatorboard 152 and a deflector board 154, shown in FIG. 1 to be locatedadjacent to each other and to illumination platform 140. It isappreciated that collimator and deflector boards 152, 154 may beprovided separate from illumination platform 140 or may be integrallyformed therewith, such that plurality of photon emitters 130 and beamshaping optical elements 150 occupy a monolithic, multi-tiered platform.Further details concerning the preferable structure and function of theilluminator assemblies formed by photon emitters 130 in conjunction withbeam shaping optical elements 150 are provided henceforth, withreference to FIGS. 5A-7.

First plurality of cameras 120 is preferably organized in a staggeredarray, comprising a series of generally parallel mutually offset rowsforming a series of staggered columns. During scanning of a substrate byoptical head 102, the substrate and optical head 102 are preferably inrelative motion along a scan direction generally indicated by an arrow156. Such motion may be by way of movement of the substrate in scandirection 156 as optical head 102 remains stationary, by way of movementof optical head 102 in scan direction 156 as the substrate remainsstationary or by way of movement of both optical head 102 and thesubstrate.

As appreciated from consideration of FIG. 1, the scan direction 156 ispreferably generally perpendicular to the direction of the rows ofcameras 120, such that the direction of the rows defines a cross-scandirection. Plurality of cameras 120 are preferably mutually spaced apartin both a scan and cross-scan direction so as to allow single-passscanning of a substrate, when the substrate and optical head 102 are inrelative motion along scan direction 156.

Here, by way of example, first plurality of cameras 120 is seen tocomprise 32 individual cameras 160 arranged in three staggered rows andcapable of providing single-pass scanning of a target. It isappreciated, however, that first plurality of cameras 120 may comprise agreater or fewer number of individual cameras 160 arranged in a varietyof array architectures, depending on the imaging requirements of opticalsystem 100. In particular, a fewer number of cameras 120 than thatillustrated may be employed, such that single-pass scanning of theentire substrate is not enabled. In such a case, movement along scandirection 156 may be complemented by a stepwise movement in thecross-scan direction, perpendicular to scan direction 156.

The arrangement and structure of plurality of cameras 120 may be bestunderstood with reference to FIGS. 2A-2C, showing a representativeportion of first plurality of cameras 120. As seen in FIGS. 2A-2C, firstplurality of cameras 120 is preferably distributed over a first 162, asecond 164 and a third 166 row in a partially overlapping arrangement asviewed in scan direction 156. As best appreciated from consideration ofFIG. 2C, such a staggered, partially overlapping arrangement of cameras160 provides a continuous lateral field of view 168 as viewed in scandirection 156, thereby allowing single-pass scanning of a target. By wayof example, the 32 camera arrangement shown herein may providesingle-pass scanning of a substrate having a width of approximately 600mm in a cross-scan direction.

As seen most clearly in FIGS. 2B and 2C, each camera 160 defines acamera axis 170 and the field of view 122 of each camera 160 is thatfield of view lying directly beneath the camera 160 and intersected bythe camera axis 170. Thus, by way of example, a first camera 172 has afirst corresponding field of view 174, a second camera 176 has a secondcorresponding field of view 178 and so forth. Circumferentialarrangements 132 of second plurality of photon emitters 130 arepreferably generally centered about and intersected by camera axis 170of each camera 160.

Each camera 160 preferably comprises a lens portion 180 and anassociated camera board 182 connected thereto. Camera board 182 may be aprinted circuit board (PCB) hosting an integrated-circuit sensor chipand electronics for camera driving and control. Camera boards 182 may beformed individually or, for manufacturing convenience, may be formed asa common element. The operation of plurality of cameras 120 may beadditionally controlled by electronic circuitry formed on a set ofcontrol boards 186. By way of example, a group of eight individualcameras 160 may be connected to and controlled by a single control board186 located posterior to the cameras 160. Control boards 186 may alsohouse electronics for the control and driving of plurality of photonemitters 130. Control boards 186 may be cooperatively coupled to cameraboards 182 so as to coordinate the operation of first plurality ofcameras 120 and second plurality of photon emitters 130.

Lens portion 180 is particularly preferably embodied as a telecentriclens. A telecentric lens suitable for use in cameras 160 may be of thetype commercially available from Schneider Optics of Bad Kreuznach,Germany; Edmund Optics of New Jersey, US; NET New Electronic TechnologyGMBH of Finning, Germany; and Opto-Engineering of Mantua, Italy.

As is known in the art, in telecentric lenses the image of the field ofview is formed by light rays propagating substantially parallel to thelens axis 170, due to the manner in which light is captured by thetelecentric lens. It is therefore understood by one skilled in the artthat it is the telecentric nature of lens portions 180 in combinationwith the generally rectangular shape of the light sensitive region ofthe image sensor of camera board 182 that give rise to the generallyrectangularly shaped fields of view 122 and the correspondingrectangularly shaped apertures 144 shown herein. It is appreciated,however, that lenses of types other than telecentric lenses may beincorporated in the first plurality of cameras 120 of the presentinvention, in which case modifications may be made as required in orderto accommodate the shapes of the fields of view associated therewith.

As best appreciated from consideration of FIG. 2B, a width of fields ofview 122 is considerably smaller than a diameter of the correspondingcamera lens 180, consistent with the telecentric nature of camera lens180. It is a particularly advantageous feature of the present inventionthat first plurality of cameras 120 is capable of providing single-passscanning of a target despite the camera fields of view beingconsiderably smaller than the camera lens diameter. By way of example,in the optical head 102 of the present invention, single pass scanningmay be achieved despite fields of view 122 having a width of the orderof approximately 20 mm less than a diameter of corresponding lenses 180.

This is in contrast to conventional single-pass optical imaging systems,in which single-pass scanning is typically enabled by the use of camerashaving fields of view at least as large as the camera lens itself.

Reference is now made to FIG. 3, which is a simplified illustration ofan arrangement of photon emitter assemblies on a portion of anillumination platform in an image acquisition device of the type shownin FIGS. 1-2C.

As seen in FIG. 3, second plurality of photon emitters 130 is arrangedin generally circumferential arrangements 132 about apertures 144 onunderside 138 of illumination board 140. Each circumferentialarrangement 132 of photon emitters 130 is preferably embodied as atleast one ring of photon emitters here comprising, by way of example, apair of mutually concentric rings of photon emitters comprising an outerring 300 and an inner ring 302. Each pair of mutually concentric outerand inner rings 300 and 302 of photon emitters 130 preferablycircumferentially surrounds a corresponding aperture 144. It isappreciated, however, that circumferential arrangements 132 of photonemitters may alternatively comprise a greater or fewer number of ringsof photon emitters surrounding each of apertures 144.

Photon emitters 130 are preferably embodied as LEDs. Preferably, LEDmembers 304 of outer ring 300 provide light of a different wavelengththan LED members 306 of inner ring 302. By way of example, LEDs 304 inouter ring 300 may be IR LEDs and LEDs 306 in inner ring 302 may beamber LEDs. It is appreciated, however, that LEDs 304, 306 respectivelycomprising inner and outer rings 300 and 302 may provide light of avariety of wavelengths and are not limited to providing light ofmutually different wavelengths. Furthermore, it is appreciated thatphoton emitters 130 are not limited to being LEDs and may comprise anyother suitable source of photons, such as diode lasers, vertical-cavitysurface-emitting lasers (VCSEL), vertical-external-cavitysurface-emitting-lasers (VECSEL), super-luminescent diodes or outputends of light emitting optical fibers.

It is a particular feature of a preferred embodiment of the presentinvention that second plurality of photon emitters 130 is arranged suchthat at least one of outer rings 300, here indicated by a ring ofstriped hatched LEDs 310, is overlapping with another one of outer rings300, here indicated by a ring of crosshatched LEDs 312. As a result ofthe mutually overlapping arrangement of neighboring outer rings 300, atleast one photon emitter member 304 of one of outer rings 300 lieswithin the generally circular boundary circumscribed by photon emittermembers 304 of another one of outer rings 300. In the case of the twoexemplary overlapping rings of photon emitters indicated by hatching inFIG. 3, it is seen that four crosshatched LEDs 312 lie within theboundary circumscribed by striped hatched LEDs 310 and four stripedhatched LEDs 310 lie within the boundary circumscribed by crosshatchedLEDs 312. As also depicted in FIG. 3, outer rings 300 may also overlapwith inner rings 302 of a neighboring field of view 144. Additionally oralternatively, neighboring ones of inner rings 302 may mutually overlap,depending on the radius thereof.

Such a multiplexed overlapping arrangement of photon emitters may occupysubstantially less volume than the volume that would be occupied by anon-multiplexed, non-overlapping arrangement of photon emitters, therebyleading to a significant reduction in the size of optical head 102. Byway of example, optical head 120 of the type illustrated in FIG. 1including 3 rows of cameras 160, may occupy a mechanical depth of180-220 mm in scan direction 156. Notwithstanding the compactness of thearrangement of the present invention, the optical head 102 of thepresent invention is preferably capable of carrying out single-passscanning of a substrate, due to the unique multiplexed arrangement ofphoton emitters 130 and partially overlapping cameras 120 employedtherein. The total depth of optical head 102 constitutes an extrasubstrate scanning length. As would be appreciated by persons skilled inthe art, the compact construction made possible by the present inventionmay translate into shorter scan travel, higher speed operation and lowercost scan stage.

Furthermore, since outer rings 300 and in certain embodiments also innerrings 302 are overlapping, the radius of each ring is less strictlylimited by space constraints on illumination board 140. Outer ring 300may have both a relatively large radius and substantially dense,azimuthally evenly spaced photon emitter placement. By way of example,each of rings 300 may have an effective optical radius in the range of80-100 mm Further by way of example, inner ring 302 may provideillumination subtending 20°-30° and outer ring 300 provide illuminationsubtending 30°-50° relative to the lens optical axis 170 at the centerof field of view 144. Overlapping outer ring 300 and inner ring 302 thusfunctionally substitute for far bulkier distinct physical ring lightassemblies, providing generally uniform, wide angle illumination offields of view 144 for a given separation between cameras 120 and plane124.

This is in contrast to conventional imaging systems, in which provisionof uniform wide angle illumination typically necessitates either a largecamera-substrate separation or an extremely expansive arrangement ofillumination sources.

By way of example, entrance facets 142 of lenses 180 of cameras 120 maybe separated from the fields of view 122 associated therewith, and hencefrom the substrate, by a distance in the range of approximately 50-100mm, taken along camera axis 170. Particularly preferably, the substratebeing imaged by cameras 120 may be separated from entrance facets 142 oflenses 180 of cameras 120 by a distance in the range of 70-90 mm Thisdistance may correspond to approximately double to quadruple the lengthof a diagonal of each field of view 122. Were rings 300 not to beoverlapping, such a separation between the cameras and fields of viewwould either necessitate an extremely large inter-camera spacing to givewide-angle illumination, or would result in very narrow or uneven angleillumination of the fields of view, both of which features would beundesirable and are avoided in the present invention.

Additionally, due at least to the close substrate-camera spacingfacilitated by the multiplexed partially overlapping arrangement ofphoton emitters in the present invention, the system of the presentinvention preferably provides high resolution images. By way of example,an optical head of the present invention may acquire images with aspatial resolution in the range of 6-30 μm (lens object-side numericalaperture in the range 0.01-0.05) and particularly preferably in therange of 8-16 μm in the green part of the visible spectrum (lensobject-side numerical aperture in the range 0.02-0.04). The provision ofhigh resolution images is a highly advantageous feature of the presentinvention and is in contrast to conventional imaging systems, in whichmuch lower resolution images are typically acquired.

It is understood that the generally circumferential arrangements 132 ofplurality of photon emitters 130, here depicted as comprising inner andouter rings 302 and 300, are not limited to being strictly circular. Inactuality, circumferential arrangements 132 of photon emitters 130 maydiverge from true circles within a tolerance of approximately ±20%.Furthermore, circumferential arrangements 132 of photon emitters 130 arenot limited to being planar. Rather, circumferential arrangements 132may be composed of photon emitters 304, 306 located at variety ofazimuthal angles with respect to fields of view 144, within a toleranceof approximately ±15°.

The illumination of fields of view 122 by plurality of photon emitters130 may be best understood with reference to FIG. 4, showing asimplified conceptual illustration of a projection of photon emittersonto a plane of fields of view 122 of plurality of cameras 120 inoptical head 102. It is appreciated that for the sake of simplicity andclarity, beam shaping elements 150 are omitted from FIG. 4 and onlyphoton emitters 130 are depicted in relation to fields of view 122.

As seen in FIG. 4, when second plurality of photon emitters 130 isprojected onto plane 124 occupied by fields of view 122, plurality ofphoton emitters 130 circumferentially surrounds fields of view 122 andneighboring outer rings 300 of photon emitters 130, such as outer rings300 formed by LEDs 310 and 312, mutually overlap.

By way of example, LEDs 310 of one of outer rings 300 direct light to afirst field of view 400 surrounded thereby, as indicated by a first setof arrows 402. LEDs 312 of another one of outer rings 300 direct lightto a second field of view 404 surrounded thereby, as indicated by asecond set of arrows 406. Due to the overlap between neighboring rings300 of LEDs 310 and 312, those of LEDs 310 lying within the boundarycircumscribed by LEDs 312 are closer to second field of view 404surrounded and illuminated by ring of LEDs 312, yet direct illuminationto the more distant first field of view 400. Similarly, those of LEDs312 lying within the boundary circumscribed by LEDs 310 are closer tothe first field of view 400 surrounded and illuminated by ring of LEDs310, yet direct illumination to the more distant second field of view404.

It is appreciated that although the architecture and operation of photonemitters 130 with respect to fields of view 122 has been describedhereinabove with respect to two particular individual fields of view 400and 404, the description hereinabove is generally applicable to otherphoton emitters and fields of view constructed and operative inaccordance with preferred embodiments of the present invention.

Reference is now made to FIGS. 5A, 5B and 5C, which are simplifiedrespective illustrations of an illumination assembly and componentsthereof, forming part of an image acquisition device of the type shownin FIGS. 1-4, constructed and operative in accordance with a preferredembodiment of the present invention;

As seen in FIGS. 5A-5C, each circumferential arrangement 132 ofplurality of photon emitters 130, here, by way of example, composed ofouter ring 300 and inner ring 302 of LEDs, lies about camera axis 170 ofcamera 160. Here, by way of example, beam shaping optical elements 150are shown to be housed by a collimator plate 500 and a deflector plate502 stacked thereon. Each circumferential arrangement 132 of photonemitters 130, in combination with corresponding beam shaping opticalelements 150 associated therewith, may be termed an illuminationassembly 504.

It is appreciated that although a single annular illumination assembly504 is illustrated in FIG. 5A, for the sake of simplicity and clarity ofdescription, in actuality, multiple ones of illumination assembly 504are preferably incorporated in optical head 102 in a multiplexed,mutually overlapping arrangement, as described hereinabove. Particularlypreferably, illumination platform 140, collimator plate 500 anddeflector plate 502 are formed as continuous, expansive elements havingmultiple, mutually overlapping arrangements of illumination assemblies504 formed thereon, as illustrated in FIGS. 1-4.

Outer ring 300 and inner ring 302 of plurality of photon emitters 130are preferably mounted on an LED mounting plate 510, as seen mostclearly in FIG. 5B showing an enlarged view thereof. Mounting plate 510preferably includes a plurality of capacitors (not shown) connected toelectrical circuitry, for controlling operation of photon emitters 130.In a preferred operational mode, photon emitters 130 are driven by shortpulses of electrical current. This allows image acquisition duringcontinuous relative motion between the optical head 102 and the scannedtarget, while minimizing image blur. Capacitors and the circuitryassociated therewith enabling such short pulse driving may be of thetype described in Chinese Patent Application No. 201510828406.3,assigned to the same assignee as the present invention and incorporatedherein by reference.

It is understood that mounting plate 510 preferably constitutes asegment of illumination platform 140. Thus, although mounting plate 510is shown herein as holding only inner and outer rings 302, 300 of photonemitters thereon, a portion of illumination platform 140 correspondingto mounting plate 510 may in actuality also host additional photonemitters, which additional photon emitters are members of other rings ofphoton emitters, encroaching on outer ring 300 and optionally also oninner ring 302.

Collimator plate 500 is preferably located immediately beneath LEDmounting plate 510 and preferably includes an array of light collimators520, each light collimator 522 of array of light collimators 520preferably cooperating with and being axially aligned with respect to acorresponding photon emitter on mounting plate 510. Here, by way ofexample, array of light collimators 520 comprises a dual-ring array,corresponding to inner and outer rings 302, 300 of photon emitters. Itis understood, however, that collimators 522 may be arranged in anysuitable configuration capable of providing the required collimation oflight emitted by plurality of photon emitters 130. It is furtherunderstood that collimator plate 500 preferably constitutes a segment ofa larger preferably planar sheet of light collimators, forming a part ofcollimator board 152.

In accordance with the specific type of photon emitter employed,collimators 522 may comprise one or more of spherical, circularlysymmetric aspherical, cylindrical or free-form lenses or reflectorsincluding Fresnel counterparts of those optical elements. By way ofexample, collimators 522 illustrated in FIG. 6 are single-elementaspheric lenses.

Deflector plate 502 is preferably located immediately beneath collimatorplate 500 and preferably includes an array of light deflectors 530, asseen most clearly in FIG. 5C showing an enlarged view thereof. Eachlight deflector 532 of array of light deflectors 530 preferablycooperates with and is located longitudinally beneath a correspondingphoton emitter 130 and collimator 522.

Each light deflector 532 preferably comprises one or more free-formoptical elements. By way of example, as seen most clearly in FIGS. 5Cand 6, light deflector 532 may be a prism having an irregularlychamfered entry facet 542 and exit facet 546. Persons skilled in the artwill recognize that facets 542 and 546 collectively function in a mannerresembling a free-form prism for deflecting light impinging thereon.Free-form facets 542 and 546 of the particular design shown in FIG. 6additionally exhibit partial light collimation functionality,complementing the collimating function of aspheric collimators 522, inorder to achieve improved illumination uniformity and efficiency at therespective field of view 122. The high deflection efficiency ofdeflector 532 in combination with collimator 522 preferably alsominimizes the escape of stray light from each photon emitter to fieldsof view other than those intended to be illuminated by each given photonemitter. It is understood that deflector plate 502 preferablyconstitutes a segment of a larger planar sheet of light deflectors,forming a part of deflector board 154.

It is understood that collimator and deflector plates 500, 502preferably each constitute only a segment of collimator and deflectorboards 152, 154 respectively. Thus, although collimator and deflectorplates 500, 502 are shown herein as holding only two rings ofcollimating and deflecting elements respectively thereon, a portion ofcollimator and deflector boards 152, 154 corresponding to collimator anddeflector plates 500, 502 may in actuality also host additionalcollimator and deflector elements respectively, which additionalcollimator and deflector elements preferably correspond to and cooperatewith photon emitters encroaching on rings of photon emitters on acorresponding portion of illumination platform 140.

LED mounting plate 510 is preferably fabricated as a printed circuitboard (PCB) on which are additionally preferably mounted some or all ofthe LED driving electronic circuitry. Alternatively, LED mounting plate510 as well as collimator plate 500 and deflector plate 502, includingthe various optical elements housed thereby, may be manufactured bythree-dimensional printing techniques (e.g. by Luximprint V.O.F of theNetherlands). Other known manufacturing techniques that may be employedfor producing collimator elements 522 and deflecting elements 532include injection molded plastic, Computer Numerical Control (CNC)machining and glass molding. It is appreciated that illuminationassemblies 504 thus are constructed of generally planar, readilymanufacturable elements, which may be produced at low cost and be easilyassembled

Each vertical stack of photon emitter 130, collimator 522 and lightdeflector 532 may be collectively termed an illumination module 550. Anexemplary illumination module 550 is illustrated in FIG. 6, light outputfrom which illumination module 550 is shown in a highly simplifiedmanner in FIG. 7. As appreciated from consideration of FIGS. 6 and 7,illumination module 550 preferably directs collimated light emitted bythe photon emitter, such as an LED, forming a part thereof towards theassociated field of view 122. Preferably, collimators 522 and deflectors532 are functional to direct light from photon emitter 130 in a mannersuch that each illumination module 550 illuminates the entirety of asingle field of view 122, as seen in FIG. 7.

It is understood that the inclusion of deflectors 532 in illuminationmodule 550 and illumination assembly 504 in order to direct collimatedlight from collimators 522 towards fields of view 122 is exemplary onlyand that deflectors 532 may be replaced by other light directingmechanisms. By way of example, deflectors 532 may be obviated and lightangled towards fields of view 122 by other mechanisms as are known inthe art. These mechanisms include but are not limited to planarrefractive beam deflectors and diffraction gratings, the latter beingparticularly effective in combination with laser type photon emitters.

It is appreciated that, in some embodiments of the present invention, itmay be advantageous for at least one illumination module of at least oneillumination assembly 504 to illuminate more than one field of view 122,rather than only a single field of view as illustrated in the case ofillumination module 550.

The illumination of more than one field of view by an illuminationmodule of the present invention may be desirable since, due to thehighly dense arrangement of photon emitters 130, individual photonemitters 130 respectively belonging to neighboring circumferentialarrangements 132 may be designated to be located at physicallyintersecting locations on illumination platform 140. As only one photonemitter may occupy a given location on illumination platform 140, thiscreates a region of conflict between two or more photon emitters 130competing to occupy at least part of the same region on illuminationplatform 140.

A conflict may arise between two or more photon emitters 130 ofneighboring inner rings 302, between two or more photon emitters 130 ofneighboring outer rings 300, or between two or more photon emitters 130of neighboring inner and outer rings 302 and 300.

Such a conflict may be resolved by shifting the location of one or moreof the photon emitters 130 competing to occupy the same position.However, this solution may not be viable in the case that the at leastone competing photon emitter requires shifting to an unacceptablydistant position from the circumferential arrangement 132 to which thephoton emitter belongs, preventing the at least one photon emitter 130from providing the required illumination to the associated field of view122.

Such a conflict may alternatively be resolved, in accordance with onepreferred embodiment of the present invention, by placing a singlephoton emitter 130 at the position of conflict on illumination platform140, the single photon emitter 130 forming part of a light-splittingillumination module directing light towards more than one field of view122. The single photon emitter 130 occupying the position of conflicteffectively replaces the multiple photon emitters that were designatedto occupy that position, by outputting light towards the fields of viewthat were designated to be illuminated by additional photon emittersoccupying that position. The single photon emitter 130 occupying theposition of conflict thus directs light to at least one other field ofview in addition to the field of view illuminated by the generallycircumferential arrangement 132 to which the photon emitter belongs.

The illumination of more than one field of view by an illuminationmodule of the present invention may be advantageous even if theabove-described conflict is not present, in order to reduce the numberof illumination modules and hence the number of photon emitters requiredon illumination platform 140. This may reduce manufacturing costs, powerdissipation and complexity in certain embodiments of the presentinvention.

Illumination module 550 may be modified so as to illuminate more thanone field of view, by replacement of single deflecting element 532 by aplurality of deflecting elements. By way of example, deflecting element532 may be replaced by a plurality of prisms having a number andorientation of facets corresponding to the number and orientation ofrequired light output beams.

Various examples of illumination modules of the present inventionconfigured to direct light towards more than one field of view, and thecorresponding light outputs therefrom, are illustrated in a highlysimplified form in FIGS. 8-12.

Turning now to FIG. 8, an illumination module 850 preferably includesphoton emitter 130, a collimating element such as collimator 522 and adeflecting element 852. It is appreciated that the collimating elementincluded in illumination module 850 is not necessarily of the samestructure as collimator 522 and may be optimized in accordance with thedesired performance characteristics of illumination module 850.Deflecting element 852 is preferably embodied as a split prism having afirst output facet 854 and a second output facet 856. First and secondoutput facets 854, 856 are preferably of mutually differentorientations, and are preferably each oriented so as to direct light toa different field of view. For example, as seen in FIG. 9, first outputfacet 854 may project an output beam towards a first field of view 860and second output facet 856 may project an output beam towards a secondfield of view 862. A third field of view 864 is preferably notilluminated by illumination module 850.

Output facets 854 and 856 of deflector element 852 are illustrated ascomprising concave surfaces in FIGS. 8 and 9. It is understood, however,that these facets may alternatively be formed as convex, outwardpointing or protruding surfaces rather than inward pointing or recessedsurfaces.

It is understood that illumination module 850 thus effectively at leastpartially replaces the functionality of two individual illuminationmodules 550 that would have illuminated first and second fields of view860 and 862 respectively.

Turning now to FIG. 10, an illumination module 1050 preferably includesphoton emitter 130, a collimator element such as collimator 522 and adeflecting element 1052. Deflecting element 1052 is preferably embodiedas a split prim having first, second and third output facets 1054, 1056and 1058. First—third output facets 1054-1058 are preferably eachorientated so as to direct light to a different field of view. Outputfacets 1054-1058 are illustrated as convex surfaces in FIG. 10. It isunderstood, however, that these facets may also be designed as concavesurfaces, as illustrated in FIG. 11. For example, as seen in FIG. 11,first output facet 1054 may direct light to first field of view 860,second output facet 1056 may direct light to second field of view 862and third output facet 1058 may direct light to third field of view 864.

It is understood that illumination module 1050 thus effectively at leastpartially replaces the functionality of three individual illuminationmodules 550 that would have illuminated first, second and third fieldsof view 860, 862 and 864, respectively.

It will be appreciated by persons skilled in the art that the splitillumination modules such as illumination modules 850 and 1050 differsomewhat in performance in comparison to a non-split illuminationmodule, such as illumination module 550. This is because each splitillumination module only projects light from a portion of the exitaperture thereof, with respect to each field of view. Additionally, thelight power of the split illumination module is distributed over morethan one field of view, resulting in the delivery of less light power toeach individual field of view illuminated thereby.

In the case of substantially diffusely reflecting substrates loss oflight power tends to be the more significant of these effects. Therelative loss of light power may be compensated for by providing aphysically larger and/or higher power photon emitter 130 within thesplit illumination module. Additionally or alternatively, the relativepower loss may be compensated for by equalizing the illumination of eachfield of view by providing additional illumination from otherlight-splitting illumination modules.

In the case of at least partially specularly reflecting substrates, theangle subtended by the illumination module may also be significant. Insuch cases, a split illumination module of the type illustrated in FIG.12 may be advantageous, in order to preserve the angular extent of theillumination.

Turning now to FIG. 12, an illumination module 1250 preferably includesphoton emitter 130, a collimating element such as collimator 522 and adeflecting element 1252. Deflecting element 1252 is preferably embodiedas multi-faceted, convex or concave, prism, directing light to multiplefields of view. The multi-prism design of deflecting element 1252 servesto evenly distribute illumination across the exit facet thereof as amultitude of small illumination gaps, which illumination gaps arescrambled by the substrate reflection properties and imaging lensacceptance angle.

It is understood that a given illumination assembly may include anycombination of illumination modules of the present invention, includingillumination modules illuminating only a single field of view andlight-splitting illumination modules illuminating multiple fields ofview, depending on the requirements of the optical inspection system inwhich the illumination assembly is incorporated.

Reference is now made to FIG. 13, which is a simplified illustration ofan optical system including an image acquisition device forming a partthereof, constructed and operative in accordance with another preferredembodiment of the present invention.

As seen in FIG. 13, there is provided an optical system 1300 includingan image acquisition device 1302. Optical system 1300 may be any type ofsystem employing optical elements and benefitting from the inclusion ofan image acquisition device therein, such as, by way of example only, anoptical scanning system, optical inspection system, optical processingsystem or optical manufacturing system. Here, by way of example, opticalsystem 1300 is shown to be embodied in a form typical of an opticalscanning system and image acquisition device 1302 to be mounted thereon.It is appreciated, however, that this representation of optical system1300 and the location of image acquisition device 1302 therein isillustrative only and may readily be varied in accordance with thedesign requirements of optical system 1300.

Image acquisition device 1302 preferably includes optical elementsoperative to illuminate a substrate handled by optical system 1300 andto subsequently acquire an image thereof. Image acquisition device 1302may therefore be termed an optical head 1302. As seen most clearly at anenlargement 1310 showing an enlarged view of optical head 1302, opticalhead 1302 preferably includes a first plurality of cameras 1320 arrangedin a mutually spaced configuration, each camera having an associatedfield of view 1322, each field of view 1322 lying in a plane such as aplane 1324. Plane 1324 preferably coincides with a surface of thesubstrate to be imaged, such that fields of view 1322 of cameras 1320lie on the substrate surface. In the case of a planar target, plane 1324occupied by the fields of view 1322 may be a common plane, within whichplane 1324 all of fields of view 1322 of cameras 1320 lie.Alternatively, in the case of a non-planar substrate to be imaged,fields of view 1322 of cameras 1320 may lie in more than one plane.

Optical head 1302 further preferably includes a second plurality ofphoton emitters 1330 arranged in a multiplicity of arrangements 1332about each camera of first plurality of cameras 1320, which photonemitters 1330 preferably illuminate fields of view 1322. Particularlypreferably, multiplicity of arrangements 1332 of photon emitters 1330are arranged about an axis 1326 of each camera of first plurality ofcameras 1320.

It is a particular feature of a preferred embodiment of the presentinvention that at least one photon emitter in at least one ofarrangements 1332 directs light to a field of view 1322 of one of thefirst plurality of cameras 1320 which is not the closest field of viewto that photon emitter. Such an arrangement of plurality of photonemitters 1330 with respect to plurality of cameras 1320 allows pluralityof photon emitters 1330 to provide wide-angle generally uniformillumination of fields of view 1322 in a highly compact form factor, asis explained in greater detail henceforth.

Second plurality of photon emitters 1330 is preferably mounted on anunderside 1338 of an illumination platform 1340. Illumination platform1340 is preferably located beneath entrance facets 1342 of lenses ofcameras 1320, interfacing cameras 1320 and fields of view 1322, withunderside 1338 of illumination platform 1340 distal from entrance facets1342. A multiplicity of apertures 1344 is preferably formed inillumination platform 1340, wherethrough light emanating fromilluminated fields of view 1322 arrives at cameras 1320. Secondplurality of photon emitters 1330 is preferably arranged with respect toapertures 1344 in a non-overlapping configuration, so as to illuminatefields of view 1322 without obscuring light emanating therefrom. Incertain embodiments photon emitters 1330 may be distributed over theentire area of illumination platform 1340 so as to maximize theillumination intensity and uniformity whilst retaining a compact formfactor.

Light emitted by plurality of photon emitters 1330 may be directedtowards fields of view 1322 in the manner described above by means ofvarious beam shaping optical elements 1350, which optical elements 1350may have collimating and/or deflecting functionalities. Such opticalelements 1350 may be mounted on one or more boards, such as a collimatorboard 1352 upon which are preferably mounted collimating elements and adeflector board 1354 upon which are preferably mounted deflectingelements. Collimator board 1352 and deflector board 1354 are shown inFIG. 13 to be located adjacent to each other and to illuminationplatform 1340. It is appreciated that collimator and deflector boards1352, 1354 may be provided separate from illumination platform 1340 ormay be integrally formed therewith, such that plurality of photonemitters 1330 and beam shaping optical elements 1350 occupy amonolithic, multi-tiered platform.

It is a particular feature of a preferred embodiment of the presentinvention illustrated in FIG. 13 that deflector board 1354 is embodiedas an array of a third plurality of axicons 1355 having light deflectingfunctionality. Array of axicons 1355 is preferably formed as a tightlypacked array of conical optical elements, typically comprising plasticor glass. As is well known in the art, axicons 1355 deflect lightsubstantially equally in all directions relative the vertical directionalong which light is incident thereon, such that no light is transmittedalong the vertical axis and a ring of deflected light is generated. Inthe embodiment of the present invention shown in FIG. 13, axicons 1355receive light from second plurality of photon emitters 1330, by way ofcollimating elements on collimator board 1352, and in turn generaterings of light illuminating fields of view 1322. The collective effectof the tightly packed array of axicons 1355 is thus to project aring-shaped radiance distributed with respect to the fields of view1322. A virtual ring illumination is thereby created with respect toeach field of view 1322, without requiring a physical circumferentialarrangement of light sources. Further details concerning the preferablestructure and function of the illuminator assemblies formed by photonemitters 1330 in conjunction with array of axicons 1355 and additionalbeam shaping optical elements 1350 are provided henceforth, withreference to FIGS. 15A-17.

First plurality of cameras 1320 is preferably organized in a staggeredarray, comprising a series of generally parallel mutually offset rowsforming a series of staggered columns. During scanning of a substrate byoptical head 1302, the substrate and optical head 1302 are preferably inrelative motion along a scan direction generally indicated by an arrow1356. Such motion may be by way of movement of the substrate in scandirection 1356 as optical head 1302 remains stationary, by way ofmovement of optical head 1302 in scan direction 1356 as the substrateremains stationary or by way of movement of both optical head 1302 andthe substrate.

As appreciated from consideration of FIG. 13, the scan direction 1356 ispreferably generally perpendicular to the direction of the rows ofcameras 1320, such that the direction of the rows defines a cross-scandirection. Cameras 1320 are preferably mutually spaced apart in both ascan and cross-scan direction so as to allow single-pass scanning of asubstrate, when the substrate and optical head 1302 are in relativemotion along scan direction 1356.

Here, by way of example, first plurality of cameras 1320 is seen tocomprise 32 individual cameras 1360 arranged in three staggered rows andcapable of providing single-pass scanning of a target. It isappreciated, however, that first plurality of cameras 1320 may comprisea greater or fewer number of individual cameras 1360 arranged in avariety of array architectures, depending on the imaging requirements ofoptical system 1300. In particular, a fewer number of cameras 1320 thanthat illustrated may be employed, such that single-pass scanning of theentire substrate is not enabled. In such a case, movement along scandirection 1356 may be complemented by a stepwise movement in thecross-scan direction, perpendicular to scan direction 1356.

The arrangement and structure of plurality of cameras 1320 may be bestunderstood with reference to FIGS. 14A-14C, showing a representativeportion of first plurality of cameras 1320. As seen in FIGS. 14A-14C,first plurality of cameras 1320 is preferably distributed over a first1362 a second 1364 and a third 1366 row in a partially overlappingarrangement as viewed in scan direction 1356. As best appreciated fromconsideration of FIG. 14C, such a staggered, partially overlappingarrangement of cameras provides a continuous lateral field of view 1368as viewed in scan direction 1356, thereby allowing single-pass scanningof a target. By way of example, the 32 camera arrangement shown hereinmay provide single-pass scanning of a substrate having a width ofapproximately 600 mm in a cross-scan direction.

As seen most clearly in FIGS. 14B and 14C, each camera 1360 definescamera axis 1326 and the field of view 1322 of each camera 1360 is thatfield of view lying directly beneath the camera 1360 and intersected bythe camera axis 1326. Thus, by way of example, a first camera 1372 has afirst corresponding field of view 1374, a second camera 1376 has asecond corresponding field of view 1378 and so forth, as seen in FIG.14B. Arrangements 1332 of second plurality of photon emitters 1330 arepreferably generally centered about and intersected by camera axis 1326of each camera 1360.

Each camera 1360 preferably comprises a lens portion 1380 and anassociated camera board 1382 connected thereto. Camera board 1382 may bea printed circuit board (PCB) hosting an integrated-circuit sensor chipand electronics for camera driving and control. Camera boards 1382 maybe formed individually or, for manufacturing convenience, may be formedas a common element. The operation of plurality of cameras 1320 may beadditionally controlled by electronic circuitry formed on a set ofcontrol boards 1386. By way of example, a group of eight individualcameras 1360 may be connected to and controlled by a single controlboard 1386 located posterior to the cameras 1360. Control boards 1386may also house electronics for the control and driving of plurality ofphoton emitters 1330. Control boards 1386 may be cooperatively coupledto camera boards 1382 so as to coordinate the operation of firstplurality of cameras 1320 and second plurality of photon emitters 1330.

Lens portion 1380 is particularly preferably embodied as a telecentriclens. A telecentric lens suitable for use in cameras 1360 may be of thetype commercially available from Schneider Optics of Bad Kreuznach,Germany; Edmund Optics of New Jersey, US; NET New Electronic TechnologyGMBH of Finning, Germany; and Opto-Engineering of Mantua, Italy.

As is known in the art, in telecentric lenses the image of the field ofview is formed by light rays propagating substantially parallel to thelens axis 1326, due to the manner in which light is captured by thetelecentric lens. It is therefore understood by one skilled in the artthat it is the telecentric nature of lens portions 1380 in combinationwith the generally rectangular shape of the light sensitive region ofthe image sensor of camera board 1382 that give rise to the generallyrectangularly shaped of fields of view 1322 and the correspondingrectangularly shaped apertures 1344 shown herein. It is appreciated,however, that lenses of types other than telecentric lenses may beincorporated in the first plurality of cameras 1320 of the presentinvention, in which case modifications may be made as required in orderto accommodate the shapes of the fields of view associated therewith.

As best appreciated from consideration of FIG. 14B, a width of fields ofview 1322 is considerably smaller than a diameter of the correspondingcamera lens 1380, in keeping with the telecentric nature of camera lens1380. It is a particularly advantageous feature of the present inventionthat first plurality of cameras 1320 is capable of providing single-passscanning of a substrate despite the camera fields of view beingconsiderably smaller than the camera lens diameter. By way of example,in the optical head 1302 of the present invention, single pass scanningmay be achieved despite fields of view 1322 having a width of the orderof approximately 20 mm less than a diameter of corresponding lenses1380.

This is in contrast to conventional single-pass optical imaging systems,in which single-pass scanning is typically enabled by the use of camerashaving fields of view at least as large as the camera lens itself.

Reference is now made to FIGS. 15A, 15B and 15C, which are simplifiedrespective illustrations of an illumination assembly and componentsthereof, forming part of an image acquisition device of the type shownin FIGS. 13-14C, constructed and operative in accordance with apreferred embodiment of the present invention;

As seen in FIGS. 15A-15C, plurality of photon emitters 1330 on a portionof illumination platform 1340 preferably surround camera axis 1326 ofcamera 1360. A collimator plate 1500 is preferably positioned beneathphoton emitters 1330 and array of axicons 1355 preferably locatedtherebeneath. Photon emitters 1330 surrounding camera 1360, incombination with corresponding beam shaping optical elements 1350associated therewith including axicons 1355, may be termed anillumination assembly 1504.

It is appreciated that although a single illumination assembly 1504 isillustrated in FIG. 15A, for the sake of simplicity and clarity ofdescription, in actuality, multiple ones of illumination assembly 1504are preferably incorporated in optical head 1302 in a multiplexed,mutually overlapping arrangement, as described hereinabove. Particularlypreferably, illumination platform 1340, collimator plate 1500 and axiconarray 1355 are preferably formed as continuous, expansive elementshaving multiple, mutually overlapping arrangements of illuminationassemblies 1504 formed thereon, as illustrated in FIGS. 13-14C.

Photon emitters 1330 are preferably mounted on an LED mounting plate1510, as seen most clearly in FIG. 15B showing an enlarged view thereof.Mounting plate 1510 preferably includes a plurality of capacitors (notshown) connected to electrical circuitry, for controlling operation ofphoton emitters 1330. In a preferred operational mode, photon emitters1330 are driven by short pulses of electrical current. This allows imageacquisition during continuous relative motion between the optical head1302 and the scanned target, while minimizing image blur. Capacitors andthe circuitry associated therewith enabling such short pulse driving maybe of the type described in Chinese Patent Application No.201510828406.3, assigned to the same assignee as the present inventionand incorporated herein by reference.

It is understood that mounting plate 1510 preferably constitutes asegment of illumination platform 1340. It is understood that theparticular geometric arrangement of photon emitters 1330 on mountingplate 1510 illustrated in FIG. 15B is exemplary only, and that photonemitters 1330 may be arranged in any suitable repeating or non-repeatingarrangement on mounting plate 1510, at least partially surroundingaperture 1344 formed therein.

Collimator plate 1500 is preferably located immediately beneath LEDmounting plate 1510 and preferably includes an array of lightcollimators 1520, each light collimator 1522 of array of lightcollimators 1520 preferably cooperating with and being locatedlongitudinally beneath a corresponding photon emitter on mounting plate1510. In actuality, when constructing illumination assembly 1504, thedensity and arrangement of photon emitters 1330 is typically set inaccordance with the practicable density with which array of lightcollimators 1520 may be constructed.

Here, by way of example, array of light collimators 1520 comprises arectangular array, corresponding to the arrangement of photon emitters1330. It is understood, however, that collimators 1522 may be arrangedin any suitable configuration capable of providing the requiredcollimation of light emitted by plurality of photon emitters 1330. Byway of example, photon emitters 1330 on plate 1510 and collimators 1522on plate 1500 may be arranged in hexagonal grids, alternative tightlypacked formations or non-regular arrays, in accordance with systemrequirements and engineering considerations. It is further understoodthat collimator plate 1500 preferably constitutes a segment of a largerpreferably planar sheet of light collimators, forming a part ofcollimator board 1352.

In accordance with the specific type of photon emitter employed,collimators 1522 may comprise one or more of spherical, circularlysymmetric aspherical, cylindrical or free-form lenses or reflectorsincluding Fresnel type counterparts of those optical elements. By way ofexample, collimator 1522 illustrated in FIGS. 15A and 16 is asingle-element aspheric lens.

Array of axicons 1355 is preferably located immediately beneathcollimator plate 1500 and preferably includes an array of lightdeflecting axicons, as seen most clearly in FIG. 15C showing an enlargedview thereof. Axicons 1355 may have a hexagonal, square or other shapedborder, in order to allow tight packing thereof into an array. Array ofaxicons 1355 is preferably but not necessarily symmetrical with respectto aperture 1344. In the embodiment of array of axicons 1355 illustratedin FIG. 15C, all of axicons 1355 are shown to be mutually identical,with the same dimensions and cone angle. It is appreciated, however,that this is exemplary only and that axicons comprising array of axicons1355 may be mutually different. For example, axicons 1355 may be ofvarious dimensions and cone angles so as to generate light rings of morethan one angle. Axicons suitable for use in the present invention may beof the type commercially available on a custom basis from JungbeckerKarl GmbH & Co., of Olpe, Germany; ALP Lighting Components Inc. ofNiles, Ill., USA; Bright View Technologies Corporation of Durham, N.C.,USA; Gaggione SAS of Montreal La Cluse, France; PowerPhotonic Ltd. ofFife, United Kingdom; and CDA GmbH of Suhl, Germany

LED mounting plate 1510 is preferably fabricated as a printed circuitboard (PCB) on which are additionally preferably mounted some or all ofthe LED driving electronic circuitry. Alternatively, LED mounting plate1510 as well as collimator plate 1500, including the various opticalelements mounted thereon, may be manufactured by three-dimensionalprinting techniques (e.g. by Luximprint V.O.F. of the Netherlands).Other known manufacturing techniques that may be employed for producingcollimator elements 1522 include injection molded plastic, ComputerNumerical Control (CNC) machining and glass molding. It is appreciatedthat illumination assemblies 1504 thus are preferably constructed ofgenerally planar, readily manufacturable elements, which may be producedat low cost and be easily assembled.

Each vertical stack of photon emitter 1330, collimator 1522 and acorresponding portion 1530 of axicon array 1355 may be collectivelytermed an illumination module 1550. An exemplary illumination module1550 is illustrated in FIG. 16, light output from which illuminationmodule 1550 is shown in a highly simplified manner in FIG. 17. Asappreciated from consideration of FIGS. 15A-17, light emitted by eachphoton emitter 1330 preferably propagates towards the correspondingcollimator element 1522, which collimator element 1522 preferablycollimates the light received thereat and produces a collimated lightoutput. The collimated light output from collimator element 1522preferably propagates towards the corresponding portion 1530 of array ofaxicons 1355.

Each axicon element in array of axicons 1355 is preferably functional togenerate light output in the form of a conical surface 1700, asillustrated in FIG. 17. Due to the highly dense arrangement of array ofaxicons 1355, array of axicons 1355 preferably generates multiple,overlapping conical surfaces or rings of light. Axicon array 1355 ispreferably structured and arranged such that the light rings generatedthereby overlap and aggregate upon fields of view 1322, therebyilluminating fields of view 1322 and minimizing the amount of straylight falling on regions between fields of view 1322.

In accordance with a particularly preferred embodiment of the presentinvention, array of axicons 1355 comprises an array of axicons formed ofmolded transparent plastic material. The plastic material may compriseone or more of acrylic, polycarbonate, cyclic olefin polymer or anyother optical grade plastic material that may be molded or shaped into adesirable optical design. Particularly, the use of polycarbonate isadvantageous due to the relatively high refractive index thereof,enabling the achievement of large deflection angles. Axicons may beconvex, as illustrated in FIGS. 15A-17. Additionally or alternatively,axicons may be concave.

Array of axicons 1355 may have a density in the range of 4-10000axicon/cm². Axicons 1355 preferably have an apex angle in the range of80° to 130° and a corresponding deflection angle in the range of29°-12.5° in the case that array of axicons 1355 comprises acrylicplastic, and in the range of 35°-15° in the case that array of axicons1355 comprises polycarbonate. It is appreciated, however, that thesevalues are illustrative only and may be readily varied by one skilled inthe art depending on the light output requirements of illuminationmodule 1550. In particular, it is appreciated that there is a trade-offbetween the number of axicons included in array of axicons 1355 and thesize of each axicon and that the design of array of axicons 1355 may beoptimized in accordance with the functional requirements thereof.

As described hereinabove, each axicon conical prism in array 1355projects a light beam propagating generally equally in all azimuthaldirections with a narrow angle relative to an axicon axis 1702. Thislight beam preferably intersects the substrate surface with ring shapedlight distribution 1700, as shown in FIG. 17. In contrast to otherpreferred embodiments of the present invention described hereinabove,the light output of array of axicons 1355 is not associated with anyparticular one of fields of view 1322. Rather, the light output of arrayof axicons 1355 is spread substantially evenly throughout the substratearea 1324 occupied by fields of view 1322. Light incident on regionsbetween fields of view 1322 is thus wasted. However, due to the tightlypacked arrangement of plurality of cameras 1320, the proportion of lightso wasted is minimized

It is appreciated that, for the sake of clarity, the light output ofonly a single axicon of the array 1355 is shown in FIG. 17. However, itis readily understood that generally similar although not necessarilyidentical light outputs are preferably projected by each axicon in array1355. The collective effect of the light output of the entirety of arrayof axicons 1355, as observed from the viewpoint of each field of view1322, is that of a ring-shaped angular spread of light having awell-defined angle relative to the axis 1326 of the telecentric lens1380.

It is a particular advantage of this embodiment of the present inventionthat the irradiance provided by array of axicons 1355 is highly uniformand substantially spatially invariant, exhibiting minimal variation inintensity at different locations within each field of view 1322illuminated thereby. The spatial invariance of the irradiance providedby array of axicons 1355 may be appreciated from consideration of FIG.18, illustrating simulation results of the angular radiance projected byan illumination arrangement of the type illustrated in FIG. 17.

As seen in FIG. 18, the simulated angular radiance as seen at the centerand corner of each of two fields of view 1322A and 1322B is plotted.Field of view 1322A is selected to lie in the middle row 1364 of theplurality of cameras 1320, whereas field of view 1322B is selected tolie in an edge row such as row 1362. As clear from a comparison of theangular radiance plots, the angular radiance as observed at variouslocations within and between each field of view 1322 is substantiallyuniform.

It is understood that the angular radiance plotted in FIG. 18 is asimulation of the radiance provided by an ideal array of axicons 1355,constructed and operative in accordance with a preferred embodiment ofthe present invention. As is appreciated by those skilled in the art, inactual practice the axicon array may comprise manufacturing variationsand tolerances. By way of example, the actual axicon apex would be offinite radius of curvature rather than infinitely sharp as simulated andadjacent axicons would typically be separated by finite transition areasrather than being immediately abutting as simulated. These manufacturingtolerances may result in the formation of gaps within the ring-shapedradiance distributions shown in FIG. 18, thus degrading the uniformityand shift invariance of the illumination.

In order to minimize the formation of gaps within the ring-shapedradiance distributions projected by array of axicons 1355 in embodimentsof the present invention, each axicon in array of axicons 1355 ispreferably of very small dimensions relative to the separation betweenarray of axicons 1355 and the corresponding fields of view 1322. By wayof example, the separation between array of axicons 1355 and fields ofview 1322 is preferably between about 10-100 times greater than adimension of the base of each axicon. As a result, angular gaps in theradiance patterns projected by array of axicons 1355 are generallyinsignificant in relation to the light scattering properties of thesubstrate and the acceptance angle of imaging lens 1380.

In accordance with certain embodiments of the present invention, arrayof axicons 1355 may comprise axicons having generally the same opticalproperties. Alternatively, array of axicons 1355 may be formed ofaxicons having mutually different geometries, such as mutually differentapex angles, and hence mutually different optical properties. By way ofexample, array of axicons 1355 may comprise interleaved axicons of twoor more mutually different geometries, projecting two or more generallyconcentric angular radiance rings of mutually different deflectionangles.

Interleaving may comprise alternating placing of a first type of axiconand a second type of axicon in accordance with a regularly ornon-regularly repeating pattern. In certain embodiments, theinterleaving may be differently structured depending on the location inrelation to camera axes 1326.

Simultaneous provision of light rings of more than one deflection anglemay be advantageous in applications where the features to be observed onthe scanned substrate comprise a number of different reflectionproperties. In such a case, light having a small incidence angle withrespect to camera axis 1326 may have the property of enhancing the edgesof generally specularly reflecting surfaces such as metals. Lightincident at relatively large angles may have the property of enhancingpoint defects such as scratches and dust particles. However, lightincident at excessively broad angles may be undesirable due to reducedoverall contrast.

It is understood that in the case that array of axicons 1355 comprisesaxicons of two or more geometries and hence deflection angles, eachaxicon of a first geometry presents a radiance gap within the angularring of light generated by each axicon of a second geometry, as observedfrom field of view 1322. By way of example, an array of axicons 1355 maycomprise a first type of axicon projecting light rings with a 15°deflection angle, interleaved with a second type of axicon projectinglight rings with a 35° deflection angle. As viewed from field of view1322 in the direction of the 35° radiance ring, each bright spot isobserved as emanating from the second type of axicon of 35° deflectionangle, located at the direction of observation. The first type of 15°deflection angle axicon, located adjacent to the 35° deflection angleaxicon, would be perceived as a dark spot in the 35° deflection angleprojected light ring, since the 15° deflection angle axicon contributesto the 15° radiance ring.

Similarly, as viewed from field of view 1322 in the direction of the 15°radiance ring, each bright spot is observed as emanating from the firsttype of axicon of 15° deflection angle, located at the direction ofobservation. The second type of 35° deflection angle axicon, locatedadjacent to the 15° deflection angle axicon, would be perceived as adark spot in the 15° deflection angle projected light ring, since the35° deflection angle axicon contributes to the 35° radiance ring.

However, provided a relatively dense array of axicons is employed, theabove-described radiance gaps may be made to be small enough to be ofnegligible significance for a given application.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly claimedhereinbelow. Rather, the scope of the invention includes variouscombinations and subcombinations of the features described hereinaboveas well as modifications and variations thereof as would occur topersons skilled in the art upon reading the forgoing description withreference to the drawings and which are not in the prior art.

1. An image acquisition device comprising: a first plurality of camerasarranged in a mutually spaced configuration, each of said cameras havinga field of view, each of said fields of view lying in a plane; and asecond plurality of photon emitters arranged in a multiplicity ofarrangements about each camera of said first plurality of cameras, atleast one of said photon emitters within said arrangements directinglight to one of said fields of view of one of said first plurality ofcameras that is not a closest of said field of views thereto.
 2. Theimage acquisition device according to claim 1, wherein said mutuallyspaced configuration of said first plurality of cameras comprises astaggered array of rows of cameras, said fields of view of said firstplurality of cameras being at least partially overlapping when viewed ina direction generally perpendicular to a direction of said rows.
 3. Theimage acquisition device according to claim 1, wherein said plane is acommon plane occupied by each of said fields of view.
 4. The imageacquisition device according to claim 3, wherein said plane coincideswith a surface of a substrate to be imaged by said image acquisitiondevice.
 5. The image acquisition device according to claim 1, whereineach of said cameras defines a camera axis, each of said arrangementsbeing centrally intersected by said camera axis.
 6. The imageacquisition device according to claim 1, wherein each of said photonemitters comprises an LED.
 7. The image acquisition device according toclaim 1, wherein each said arrangement comprises at least one ring ofphoton emitters.
 8. The image acquisition device according to claim 7,wherein said at least one ring of photon emitters comprises an innerring of photon emitters and an outer ring of photon emitters, said innerand said outer rings being generally concentric.
 9. The imageacquisition device according to claim 8, wherein said inner ring emitslight of a first wavelength and said outer ring emits light of a secondwavelength, said first and said second wavelengths being mutuallydifferent.
 10. The image acquisition device according to claim 9,wherein said inner ring includes IR LEDs and said outer ring areincludes amber LEDs.
 11. The image acquisition device according to claim1, wherein said field of view to which light is directed by one of saidphoton emitters is entirely illuminated by said one of said photonemitters.
 12. The image acquisition device according to claim 1, furthercomprising an illumination platform having an upper surface and a lowersurface, said upper surface being proximal to said first plurality ofcameras, said lower surface being distal from said first plurality ofcameras, said second plurality of photon emitters being mounted on saidlower surface.
 13. The image acquisition device according to claim 12,wherein a multiplicity of apertures is formed in said illuminationplatform, each of said apertures allowing viewing therethrough of saidfield of view by one of said cameras.
 14. The image acquisition deviceaccording to claim 13, wherein each of said arrangements of photonemitters circumferentially surrounds each of said apertures.
 15. Theimage acquisition device according to claim 14, wherein each of saidcameras comprises a telecentric lens.
 16. The image acquisition deviceaccording to claim 15, wherein each of said apertures is generallyrectangular.
 17. The image acquisition device according to claim 12,further comprising at least one collimator for collimating said light.18. The image acquisition device according to claim 17, wherein said atleast one collimator is mounted on a collimator board.
 19. The imageacquisition device according to claim 18, wherein said collimator boardis located adjacent to said illumination platform, between saidillumination platform and said plane.
 20. The image acquisition deviceaccording to claim 19, further comprising at least one deflectingelement for directing said light output by said at least one collimator.21. The image acquisition device according to claim 20, wherein said atleast one deflecting element is mounted on a deflector board.
 22. Theimage acquisition device according to claim 21, wherein said deflectorboard is located abutting said collimator board.
 23. The imageacquisition device according to claim 20, wherein said deflector boardis formed monolithically with said collimator board.
 24. The imageacquisition device according to claim 20, wherein said at least onedeflecting element directs said light output towards a single field ofview.
 25. The image acquisition device according to claim 20, whereinsaid at least one deflecting element directs said light output towardsmore than one field of view. 26-43. (canceled)
 44. The image acquisitiondevice according to claim 17, further comprising at least one deflectingelement coupled to said at least one collimator. 45-47. (canceled) 48.The image acquisition device according to claim 44, wherein said atleast one collimator is coupled to said at least one photon emitter ofsaid arrangement directing light to at least one other field of view inaddition to said field of view illuminated by said arrangement, said atleast one deflecting element directing said light to said at least oneother field of view in addition to said field of view illuminated bysaid arrangement.
 49. The image acquisition device according to claim48, wherein said at least one deflecting element comprises at least oneprism having a plurality of exit facets angled to direct said lighttowards said at least one other field of view in addition to said fieldof view illuminated by said arrangement. 50-57. (canceled)
 58. The imageacquisition device according to claim 13, wherein each of saidarrangements of photon emitters surrounds each of said apertures. 59-64.(canceled)
 65. The image acquisition device according to claim 20,wherein said at least one deflecting element comprises a third pluralityof axicons.
 66. The image acquisition device according to claim 65,wherein said third plurality of axicons comprises an array of axiconshaving a density of between 4-10000 axicons/cm².
 67. The imageacquisition device according to claim 65, wherein said third pluralityof axicons comprises axicons having mutually similar optical properties.68. The image acquisition device according to claim 65, wherein saidthird plurality of axicons comprises axicons having mutually differentoptical properties.
 69. The image acquisition device according to claim1, wherein each of said arrangements illuminates one of said fields ofview, wherein each of said arrangements, when projected on said plane ofsaid field of view illuminated thereby, circumferentially surrounds saidfield of view.
 70. The image acquisition device according to claim 1,wherein said multiplicity of arrangements are generally circumferential.